Neon or nitrogen (3)
I believe the answer is:
gas
I believe this is a double definition.
'neon' is the first definition.
(I've seen this in another clue)
'nitrogen' is the second definition.
(thesaurus)
(Other definitions for gas that I've seen before include "State of matter not solid or liquid" , "Hydrogen or methane, say" , "Substance like air" , "Nitrogen, say" , "natural resource" .)